Project Summary: Trauma is the leading cause of death in young people worldwide and has an estimated annual healthcare cost of 400 billion dollars per year in the United States alone. Survivors of trauma suffer from severe morbidity in the form of organ failure and thromboembolic complications, which are driven, in large part, by excessive inflammation and a vicious cascade of coagulation abnormalities. The lack of understanding of the mechanisms that regulate inflammation and coagulopathy following trauma present a major international health problem, as the lack of therapeutic targets severely limits the ability to intervene. As such, understanding the link between trauma, inflammation and coagulopathy is the key to developing strategies to help prevent organ failure and morbidity in the millions of annual survivors of trauma. Our lab has recently made great strides towards understanding a potential link. We have identified that signalling through the key innate immune receptor, toll-like receptor 4 (TLR4) on platelets is responsible, in part, for both excessive inflammation and coagulopathy following severe hemorrhage in mice. These findings are a key early advance in the field, as platelets serve as both the initial responders in hemostasis but also as early, key effector cells in the initiation of inflammation. Despite these discoveries, the ligand that triggers this platelet `dysfunction' through TLR4 is unknown. Importantly, severe trauma is known to activate the innate immune system through a release of high quantities of danger associated molecular pattern molecules (DAMPs). The present proposal is based on the hypothesis that high-mobility group box 1 (HMGB1), a key DAMP and well characterized TLR4 ligand, is released specifically by platelets following trauma and regulates both the coagulation abnormalities seen after trauma by paracrine signalling on adjacent platelets at the site of developing thrombus as well as excessive inflammation through signalling to neutrophils and other inflammatory cells. We seek to address 3 key challenges related to this hypothesis. The first involves understanding the mechanisms by which HMGB1 promotes thrombosis through examining effects on key platelet adhesion molecules. The second examines the role of platelet HMGB1 in neutrophil activation and production of neutrophil extracellular traps (NETs) following trauma and the role of platelet-HMGB1 mediated NET production in acute lung injury. Finally, we propose the novel and innovative approach of using a TLR4 inhibitor that we have recently patented (US #9,072.760) and HMGB1 inhibitors packaged into a platelet-mimicking drug delivery nanovector for specific targeting of activated platelets at the site of inflammation and developing thrombus.